I. Field of the Invention
This invention relates to optical detectors, in particular to optical detectors incorporating optical filters, and more particularly to such detector and filter combinations suitable for use in optical communications.
II. Prior Art and Other Considerations
Optical communications systems employing optical fibres as the transmission medium are increasingly widely used. Such systems are now routinely being incorporated in national and international telecommunications networks.
There is an increasing desire to employ wavelength division multiplexing (WDM) techniques to increase the useful capacity of optical fibre links. WDM transmitters routinely comprise a plurality of narrow-linewidth semiconductor lasers, the operating wavelengths of the different lasers being suitable spaced apart. WDM demultiplexers or receivers employ either gratings or dielectric transmission filters to separate the various optical wavelengths. A disadvantage of such demultiplexers is that precise alignment of their many components is required, and this, together with the high cost of components such as gratings, makes such demultiplexers unsuitable for mass production, thereby inhibiting the widespread adoption of WDM systems.
The present invention seeks to facilitate the mass production of WDM demultiplexers and receivers.